US20080071248A1

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Publication number: US20080071248A1
Application number: US11/854,765
Authority: US
Inventors: Jessie Delgado; Kevin Magrini; Benjamin Fruland
Original assignee: Cardiac Pacemakers Inc
Current assignee: Cardiac Pacemakers Inc
Priority date: 2006-09-15
Filing date: 2007-09-13
Publication date: 2008-03-20

Abstract

A delivery system for deploying an implantable sensor assembly at an implantation site in a patient, the sensor assembly including a sensor element and an anchor. The delivery system includes an outer catheter, an elongate, tubular first inner member movable within the outer catheter, and a retaining element disposed within the first inner member and adapted to releasably engage the sensor assembly during delivery. In one embodiment, the first inner member has a distal end portion including a sheath sized to receive the sensor assembly and retain the anchor in a collapsed delivery configuration. In another embodiment, the first inner member includes a distal end portion including a socket sized to releasably retain a portion of the sensor during delivery.

Description

CROSS REFERENCE TO RELATED APPLICATION

The present application claims priority under 35 U.S.C. §119 to U.S. Provisional Application No. 60/844,953, filed Sep. 15, 2006, entitled “DELIVERY SYSTEM FOR AN IMPLANTABLE PHYSIOLOGIC SENSOR” which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to medical devices and methods for anchoring implantable medical devices in the body. In particular, the present invention is a delivery system for accurately delivering implantable physiologic sensors to implantation sites within a patient's cardiovascular system.

BACKGROUND

Medical devices are known that can be implanted within a patient's body for monitoring one or more physiological parameters and/or for providing therapeutic functions. For example, sensors or transducers can be placed in the body for monitoring a variety of properties, such as temperature, blood pressure, strain, fluid flow, chemical properties, electrical properties, magnetic properties, and the like. In addition, medical devices can be implanted that perform one or more therapeutic functions, such as drug delivery, cardiac pacing, defibrillation, electrical stimulation, and the like.

One parameter of particular interest is blood pressure. One or more implantable pressure sensing modules can be used in conjunction with cardiac rhythm management (CRM) devices to facilitate optimization of CRM device settings. In such systems, the pressure sensing module is delivered transvenously to a target vessel (e.g., the pulmonary artery) and anchored in the vessel using various fixation techniques. Accurate placement of the sensing module is an important factor in accurately and reliably measuring the desired parameter. Additionally, under some circumstances, it becomes necessary to re-position an implantable sensor module after initial deployment or, alternatively, to remove the sensor from the patient entirely.

Thus, a need exists for apparatus and methods for accurately delivering and deploying implantable medical devices within a patient's body. In particular, there is a need for a delivery system and method for accurately delivering implantable pressure sensing devices within a patient's vasculature system.

SUMMARY

The present invention, in one embodiment, is a system for deploying an implantable sensor assembly at an implantation site in a patient, the sensor assembly including a sensor element and an anchor. The system comprises an outer catheter, an elongate, tubular first inner member, and a retaining element slidably disposed within the first inner member. The first inner member has a distal end portion terminating in a distal opening, the distal end portion sized to receive at least a portion of the sensor assembly for delivery of the sensor assembly to the implantation site. The retaining element includes an elongate body having a distal end, a sensor engagement structure on the distal end of the body adapted to releasably engage the sensor assembly, and an actuating member slidably coupled to the body and adapted to cause the sensor engagement structure to engage the sensor.

The present invention, in another embodiment, is a delivery system for an implantable sensor assembly including a sensor and a self-expanding anchor. The system comprises an outer catheter having an internal diameter sized to receive the sensor assembly, an elongate, tubular first inner member movable within the outer catheter, and means slidable within the first inner member for releasably engaging the sensor. The first inner member has a distal end portion terminating in a distal opening, the distal end portion sized to receive at least a portion of the sensor assembly for delivery of the sensor assembly to an implantation site.

In yet another embodiment, the present invention is a method of implanting an implantable sensor assembly at an implantation location in a vasculature system of a patient, the sensor assembly including a sensor and a self-expanding anchor. The method comprises transvenously advancing a catheter into the vasculature system such that a distal end of the catheter is positioned proximate the implantation location. Next, the method includes advancing the sensor assembly through a lumen of the catheter to the implantation location, the sensor assembly releasably retained at a distal end of a delivery device that includes an elongate, tubular first inner member movable within the catheter and having a distal end portion terminating in a distal opening, the distal end portion sized to receive at least a portion of the sensor assembly for delivery of the sensor assembly to the implantation site, and an elongate retaining element disposed within the first inner member. The method next includes deploying the sensor assembly from the distal opening of the first inner member with the retaining element releasably coupled to the sensor assembly, and de-coupling the retaining element from the sensor assembly.

While multiple embodiments are disclosed, still other embodiments of the present invention will become apparent to those skilled in the art from the following detailed description, which shows and describes illustrative embodiments of the invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not restrictive.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view of a delivery system for delivering an implantable medical device, which in the illustrated embodiment is an implantable sensor assembly, to an implantation site within a pulmonary artery of a heart according to one embodiment of the present invention.

FIG. 2 is a partial cutaway perspective view of the distal portion of the delivery system ofFIG. 1.

FIGS. 3-5 are partial cross-sectional views of the distal portions of an inner member and a retaining element of the delivery system ofFIG. 1.

FIG. 6 is a partial cutaway view of a distal portion of an implantable sensor delivery system according to another embodiment of the present invention.

FIGS. 7-10 are perspective views illustrating a sensor assembly being deployed using the implantable sensor assembly delivery system ofFIG. 6.

While the invention is amenable to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and are described in detail below. The intention, however, is not to limit the invention to the particular embodiments described. On the contrary, the invention is intended to cover all modifications, equivalents, and alternatives falling within the scope of the invention as defined by the appended claims.

DETAILED DESCRIPTION

FIG. 1 shows adelivery system10 for delivering an implantable medical device, which in the illustrated embodiment is animplantable sensor assembly12, to a target implantation site within apulmonary artery16 of aheart20 according to one embodiment of the present invention. As shown, theheart20 generally includes asuperior vena cava22, aright atrium24, aright ventricle26, aventricular septum28, a rightventricular outflow tract30, aleft ventricle32 and aleft atrium34. As shown, the rightventricular outflow tract30 leads to thepulmonary artery16, which is separated from the right ventricle by apulmonary artery valve38.

Thedelivery system10 is sized (i.e., has a length and diameter) to navigate the patient's vasculature to the target implantation site from a location external to the patient's body. In the illustrated embodiment, thedelivery system10 enters theheart20 through thesuperior vena cava22, and extends through theright atrium24 and the rightventricular outflow tract30 to deliver theimplantable sensor assembly12 in the mainpulmonary artery16. In such an embodiment, thedelivery system10 may be transvenously advanced to theheart20 by any methods known in the art. For example, as is well known, thedelivery system10 may enter the patient's vasculature system through a percutaneous incision into the left subclavian vein, the left axillary vein, the left internal or external jugular vein, the left brachiocephalic vein, or through a femoral approach. In various embodiments, thedelivery system10 may be used to deliver animplantable sensor assembly12 to a branch of the pulmonary artery16 (e.g., the right or left pulmonary artery, not shown). In other embodiments, thedelivery system10 may be used to deliver an implantable sensor assembly to other areas of the patient's vasculature.

As shown inFIG. 1, thedelivery system10 includes a flexible, elongateouter catheter40, a flexible, elongateinner member44 disposed within theouter catheter40, and a flexible,elongate retaining element48 disposed within theinner member44 and releasably engaged with thesensor assembly12. The outer catheter includes aproximal end56 and adistal end60. As will be appreciated, theouter catheter40 includes at least one lumen (not shown inFIG. 1) through which theinner member44 is disposed. As will be explained in detail below, thedelivery system10, and other embodiments of the present invention, advantageously provides accurate control over the implantation location of thesensor assembly12. Additionally, the delivery systems of the present invention allow the physician to re-position and re-deploy thesensor assembly12 if necessary or desired.

Theouter catheter40 and theinner member44 are movable relative to each other, and theretaining element48 is movable relative to theinner member44, to deploy thesensor assembly12 at the target implantation site. In the illustrated embodiment, thedelivery system10 includes acontrol mechanism64 on theproximal end56 of theouter catheter40 and which is operatively coupled to at least theinner member44. Thecontrol mechanism64 is operable to allow a physician to control relative movement of at least the outer catheter and

inner member

40,44, and in some embodiments, theretaining element48, for delivery and deployment of thesensor assembly12. Thecontrol mechanism64 may include any mechanism or structure known or later developed for controlling the relative longitudinal and/or rotational movement of inner and outer catheters of a dual catheter system. In one exemplary embodiment, thecontrol mechanism64 includes a thumbwheel operatively coupled to theinner member44 to permit the physician to slide theinner member44 within theouter catheter40.

Theouter catheter40 can be any catheter known in the art or later developed for accessing a target implantation location in a patient's vasculature. As will be appreciated, the particular design and construction, including materials, of theouter catheter40 is determined based on the needs of the patient, and in particular, the selected implantation location for theimplantable sensor assembly12. In one embodiment, theouter catheter40 is a catheter configured for accessing thepulmonary artery16 or a branch thereof. In one embodiment, theouter catheter40 can be advanced to thepulmonary artery16 over a guidewire positioned therein through a Swan Ganz procedure, in which a balloon catheter is inserted into the venous system and floated with the blood flow into and through theheart20 out to thepulmonary artery16.

As shown inFIG. 1, thesensor assembly12 includes animplantable sensor70 and ananchor74 coupled to thesensor70. As will be discussed in more detail below, theanchor74 is an expandable structure configured to assume a collapsed configuration for transvenous delivery of thesensor assembly12 to the desired implantation location through thedelivery system10, and an expanded configuration, illustrated inFIG. 1, in which theanchor74 engages aninner surface76 of thepulmonary artery16.

Thesensor70 may be configured to perform one or more designated functions, which may include taking one or more physiological measurements. Thesensor70 may be configured to measure any known physiologic parameters such as, for example, blood pressure, temperature, blood or fluid flow, strain, electrical, chemical, or magnetic properties within the body. The specific parameters to be measured, and thus the implantation site for thesensor assembly12, are determined based on the particular therapeutic needs of the patient. In one exemplary embodiment, thesensor70 may be configured to measure blood pressure in the pulmonary artery16 (e.g., as illustrated inFIG. 1). In one embodiment, thesensor70 may further be adapted to store and/or transmit blood pressure data to another implanted device (e.g., a cardiac rhythm management device such as a pacemaker, not shown) and/or a device (e.g., a monitor or programmer) located external to the patient's body.

In various embodiments, thesensor70 is configured to communicate with other devices, such as an external device or another implantable medical device (e.g., a pacemaker and/or defibrillator) via a wireless communication link. Various types of wireless communication circuitry are well known in the art, and the specific type and/or style of wireless communication that can be used is not limited. For example, ultrasonic waves, acoustic communications, radio frequency communications, and the like may be used. In one embodiment, thesensor70 includes an acoustic transmitter/receiver configured for acoustic telemetry.

FIG. 2 is a perspective view of the distal portion of thedelivery system10 showing a partial cutaway of theinner member44, and further showing theimplantable sensor assembly12 releasably coupled to the retainingelement48 for delivery of thesensor assembly12. As shown inFIG. 2, theouter catheter40 includes alumen84 sized to slidably receive theinner member44, and terminates in adistal opening88. As further shown inFIG. 2, theinner member44 includes adistal end portion92 in the form of a sheath having adistal opening96 and an inner diameter and length sized to receive thesensor assembly12 so as to maintain theanchor74 of thesensor assembly12 in a collapsed configuration during delivery.

As can further be seen inFIG. 2, the retainingelement48 includes abody102 having adistal end106, a plurality ofdeflectable jaw members110 extending distally from thedistal end106, and a tubular actuating member114 (shown in cutaway view to illustrate the body102) slidably disposed over thebody102. Thejaw members110 operate as a sensor engagement structure for releasably engaging a portion of thesensor70. As will be explained in more detail below, thejaw members110 are naturally biased radially outwardly in an undeflected state, and the actuatingmember114 is configured to force thejaw members110 radially inward so as to engage thesensor assembly12 by clamping onto thesensor assembly12.

In the illustrated embodiment, thesensor70 includes ahub116 at its proximal end. As shown, thehub116 is configured to mate with thejaw member110 to promote positive coupling of the retainingelement48 and thesensor70. In other embodiments, a different engagement feature may be included on thesensor12. In other embodiments, thehub116 or other engagement feature may be omitted.

In various embodiments, the retainingelement48 may include different sensor engagement structures. For example, in one embodiment, the retainingelement48 may include an elongated tether having a hook at its distal end, which hook is adapted to engage an aperture or loop on thesensor70. Other embodiments may incorporate still other sensor engagement structures. In still other embodiments, the retainingelement48 is simply a solid or tubular structure (i.e., lacks thejaw members110 and actuating member114), and can be used to push thesensor assembly12 distally and/or resist proximal displacement of thesensor assembly12.

Theinner member44 and the retainingelement48 are dimensioned so as to extend proximally from the implantation location (e.g., a location within thepulmonary artery16 as shown inFIG. 1) to or near theproximal end56 of theouter catheter40. Additionally, as shown inFIG. 2, theouter catheter40 can be retracted proximally relative to theinner member40, or alternatively, the inner member44 (with thesensor assembly12 retained therein) can be advanced distally relative to theouter catheter40, such that thesensor assembly12 may be deployed from thedistal opening96 of theinner member40 without interference from theouter catheter40.

Theouter catheter40 is sized to accommodate the selected implantable sensor assembly12 (or other implantable device), and as will be appreciated, has a length sufficient to transvenously deliver thesensor assembly12 to the desired implantation site through a percutaneous access site such as described above. In various exemplary embodiments, theouter catheter40 may range in size from a 6 French to a 20 French guide catheter. In some embodiments, for example, where thesensor assembly12 is configured for implantation in thepulmonary artery16, theouter catheter40 may range in size from 10 French to 16 French.

Theinner member44 may be made from substantially the same or identical materials as theouter catheter40. In some embodiments, theinner member44 may be made substantially from a braided composite tubing as is known in the art for catheters and the like. In some embodiments, thedistal end portion92 of theinner member44 may be made from a relatively low durometer material such as, for example, low-durometer Pebax. In other embodiments, the inner surface of thedistal end portion92 may include a biocompatible, lubricious coating to facilitate relative displacement of theinner member44 and thesensor assembly12 without undue friction.

The materials selected for the retainingelement48 are not of particular significance. In some embodiments, thebody102 and/or the actuatingmember114 may be made from a metal (e.g., stainless steel) or a polymeric material. In some embodiments, thejaw members110 may be made from materials exhibiting shape memory and/or superelastic properties, such as, for example, Nitinol or any of a number of other shape memory alloys or polymers. In some embodiments, the retainingelement48 may include a radio-opaque marker at or near its distal end.

FIGS. 3-5 are partial cross-sectional views of the distal portions of theinner member44 and the retainingelement48 illustrating the deployment of thesensor assembly12 from theinner member44 according to one embodiment of the present invention. It will be appreciated that theouter catheter40 has already been retracted proximally relative to theinner member44, such as is shown inFIG. 2. As shown inFIG. 3, thesensor assembly12 is initially fully retained within thedistal end portion92 of theinner member40, with theanchor74 in the collapsed configuration. As further shown inFIG. 3, the actuatingmember114 of the retainingelement48 is positioned at least partially over thejaw members110, thereby clamping thejaw members110 onto theproximal hub116 of thesensor70. As explained above, however, in other embodiments, thejaw members110 may engage other engagement features of thesensor assembly12. Alternatively, the engagement feature may be omitted, and the jaw members may engage other portions of the sensor assembly12 (e.g., the housing of thesensor70 or a portion of the anchor74).

InFIG. 4, theinner member44 has been moved proximally relative to thesensor assembly12 so as to release the sensor assembly12 (or at a minimum, the anchor74) from thedistal end portion92 of theinner member44. With theinner member44 so positioned, theanchor74 is permitted to expand to an expanded configuration for frictionally engaging an inner surface of the target vessel (e.g., the pulmonary artery, seeFIG. 1) to secure thesensor assembly12 therein. Theanchor74 may be a self-expanding anchor having a stent-like structure similar to known cardiovascular stents. Alternatively, theanchor74 may be expandable by other means (e.g., by a balloon). In various embodiments, theanchor74 may be any of the anchoring structures disclosed in co-pending and commonly assigned U.S. patent application Ser. No. 11/216,738 titled “DEVICES AND METHODS FOR POSITIONING AND ANCHORING IMPLANTABLE SENSOR DEVICES” filed Aug. 31, 2005, and U.S. Provisional Application No. 60/844.821 titled “ANCHOR FOR AN IMPLANTABLE SENSOR” filed Sep. 15, 2006. The contents of the foregoing pending applications are incorporated herein by reference for all purposes.

As shown inFIG. 4, the retainingelement48 can remain coupled to thesensor assembly12 after deployment of theanchor74 from thedistal end portion92 of theinner member44. This permits thesensor assembly12 to be repositioned to another location within the target vessel, or another area of the patient's vasculature, if desired. For example, it may be desirable to perform various diagnostic tests on thesensor70 to confirm that it is functioning properly and/or that the chosen implantation location is suitable. Alternatively, or additionally, the physician may wish to confirm that thesensor assembly12 is sufficiently secured at the implantation site before releasing the retainingelement48. In particular, where theanchor74 is one of the re-positionable anchor structures disclosed in co-pending and commonly assigned U.S. Provisional Application No. 60/844,821 titled “ANCHOR FOR AN IMPLANTABLE SENSOR”, thesensor assembly12, including theanchor74, can be retracted within thedistal end portion92 of theinner member44 by pulling proximally on the retainingelement48 while holding theinner member44 in place. Theinner member44, with thesensor assembly12 retained therein, can then be re-positioned within the target vessel, and thesensor assembly12 re-deployed as described above. Alternatively, theinner member44 may be retracted back within the outer catheter40 (seeFIG. 2), and the entire delivery system can be re-located to a different target implantation site, or can be removed from the patient entirely.

FIG. 5 illustrates thesensor assembly12 after being de-coupled from the retainingelement48. As shown inFIG. 5, with the actuatingmember114 retracted proximally, thejaw members110 are allowed to resume their undeflected configuration and disengage from thehub116.

FIG. 6 is a partial cutaway view of a distal portion of an implantablesensor delivery system210 and animplantable sensor assembly212 coupled thereto according to another embodiment of the present invention. As shown inFIG. 6, thedelivery system210 includes an elongateouter catheter240, an elongateinner member244, and anelongate retaining element248. As further shown inFIG. 6, like thesensor assembly12 described above, thesensor assembly212 includes asensor element270 and ananchor portion274. In the illustrated embodiment, thesensor270 includes aproximal portion275 releasably engaged by and received by theinner member244.

As shown, the outer catheter includes alumen284 sized to slidably receive theinner member244, and terminates in adistal opening288. Theouter catheter240 may be of substantially the same construction as theouter catheter40 described above. In the illustrated embodiment, theouter catheter240 includes a radio-opaque end portion289, which may optionally include an a traumatic tip. In other embodiments, the radio-opaque portion289 is omitted.

As further shown inFIG. 6, theinner member244 is generally tubular and includes adistal end portion292 including asocket294 having adistal opening296 and an inner diameter and length sized to receive and frictionally engage at least a portion, (i.e., in the illustrated embodiment, the proximal portion275) of thesensor270. Thus, unlike thedistal end portion92 of theinner member44 described above, thedistal end portion292 is not sized to receive theentire sensor assembly212, and in particular, theanchor portion274 of thesensor assembly212. Rather, in the embodiment illustrated inFIG. 6, theanchor portion274 is retained in its collapsed configuration for delivery by theouter catheter240. Theouter catheter240 and/or theinner member244 may include at or near their proximal ends (not shown) a control mechanism similar or identical to those described above in connection with thedelivery system10.

In one embodiment, the sensorproximal end portion275 may be held within thesocket294 by an interference fit. In such embodiments, the inner diameter of thesocket294 may be sized to be from about 0.002 inches to about 0.004 inches smaller than the outer diameter of the sensorproximal end portion275, to ensure sufficient frictional engagement of thesensor270 during delivery. In another embodiment, a relatively weak adhesive bond may be utilized to releasably retain the sensorproximal end portion275 within thesocket294.

FIGS. 7-10 illustrate thesensor assembly212 being deployed using the implantable sensorassembly delivery system210 according to one embodiment of the present invention. For the purpose of this description only, theanchor274 is not shown inFIGS. 7-10. It is emphasized that thesensor assembly212 shown inFIGS. 7-10, however, may also include theanchor274, which may be a self-expanding anchor similar or identical to those described above with respect to theanchor74.

As shown inFIG. 7, thedistal end portion292 can be displaced distally with respect to theouter catheter240. This can be accomplished by maintaining theouter catheter240 in place and distally advancing the inner member244 (e.g., by use of a control mechanism operatively coupled to one or both of theouter catheter240 and the inner member244). Alternatively, or additionally, theinner member244 may be held in place while theouter catheter240 is retracted proximally. In either case, thesensor assembly212 can be deployed out of thedistal opening288 with theproximal portion275 of thesensor270 retained within thesocket294 of theinner member244. It will be appreciated that the anchor274 (not shown) may then be expanded, or will self-expand, upon being deployed from thedistal opening288 of theouter catheter240.

FIGS. 8-9 illustrate thedelivery system210 with thesensor assembly212 displaced distally from thedistal opening296 of thesocket294, with the retainingelement248 still releasably coupled to thesensor270. Such displacement can be accomplished, for example, by maintaining thesensor assembly212 in position using the retainingelement248 and simultaneously retracting the inner member244 (e.g., by operating a control mechanism such as a thumbwheel, not shown, coupled to the inner member244). Alternatively, or additionally, and particularly if the anchor (not shown) has not yet significantly engaged with the target vessel tissue, theinner member244 may be maintained in position while the retainingelement248, and accordingly, thesensor assembly212, are pushed in the distal direction. As shown inFIG. 9, theinner member244 can, in some embodiments, be fully retracted within theouter catheter240 with the retaining element still coupled to thesensor270.

FIG. 10 illustrates thedelivery system210 with the retainingelement248 fully disengaged and de-coupled from thesensor assembly212 and partially retracted back within theinner member244 andouter catheter240. In the illustrated embodiment, the retainingelement248 is shown to be substantially similar to the retainingelement48 above, and includes aninner body member402 including a plurality ofdistal jaw members410, and anouter actuating member414 disposed over thebody member402 for causing thejaw members410 to engage thesensor270. Again, however, any structure or mechanism capable of releasably engaging and retaining thesensor assembly212 as necessary for the particular deployment technique used can be incorporated into the retainingelement248.

As previously discussed, theouter catheter240, theinner member244, and/or the retainingelement248 may, in various embodiments, be of substantially the same or identical construction as theouter catheter40, theinner member44, and the retainingelement48 described above. In some embodiments, all or part of thedistal end portion292, including thesocket294, may be of a relatively low durometer material, e.g., low durometer Pebax, as compared to other portions of theinner member244. Such configurations advantageously promote positive engagement of the sensorproximal end portion275 within thesocket294, yet still permit thesensor270 to be released from thesocket294 without requiring undue force.

Various modifications and additions can be made to the exemplary embodiments discussed without departing from the scope of the present invention. For example, while the embodiments described above refer to particular features, the scope of this invention also includes embodiments having different combinations of features and embodiments that do not include all of the described features. Accordingly, the scope of the present invention is intended to embrace all such alternatives, modifications, and variations as fall within the scope of the claims, together with all equivalents thereof.

Claims

1. A system for deploying an implantable sensor assembly at an implantation site in a patient, the sensor assembly including a sensor element and an anchor, the system comprising:

an outer catheter;

an elongate, tubular first inner member movable within the outer catheter and having a distal end portion terminating in a distal opening, the distal end portion sized to receive at least a portion of the sensor assembly for delivery of the sensor assembly to the implantation site; and

a retaining element slidably disposed within the first inner member, the retaining element including:

an elongate body having a distal end;

a sensor engagement structure on the distal end of the body adapted to releasably engage the sensor assembly; and

an actuating member slidably coupled to the body and adapted to cause the sensor engagement structure to engage the sensor.

2. The system ofclaim 1 wherein the sensor engagement structure of the retaining element includes a plurality of deflectable jaw members extending distally from the distal end of the body, and the actuating member is adapted to deflect the jaw members to cause the jaw members to engage the sensor.

3. The system ofclaim 1 wherein the first inner member and the retaining element are movable relative to each other and have lengths selected such that the distal end of the retaining element can extend to the distal opening of the first inner member to cause the sensor assembly to be released from the distal opening of the first inner member.

4. The system ofclaim 1 wherein the first inner member is a generally tubular sheath, and wherein the distal end portion is sized to receive the sensor and the anchor for delivery of the sensor assembly to the implantation site.

5. The system ofclaim 4 wherein the anchor has a radially collapsed delivery configuration and a radially expanded implanted configuration, and wherein the distal end portion of the sheath is adapted to retain the anchor in the radially collapsed configuration for delivery of the sensor assembly to the implantation site.

6. The system ofclaim 5 wherein the sheath is adapted to be retracted proximally relative to the retaining element and the anchor to allow the anchor to assume its radially expanded implanted configuration.

7. The system ofclaim 6 wherein the retaining element is adapted to retain the sensor assembly in position as the sheath is retracted proximally.

8. The system ofclaim 1 wherein the distal end portion of the first inner member includes a socket adapted to releasably retain the sensor for delivery of the sensor assembly to the implantation site.

9. The system ofclaim 8 wherein the outer catheter is sized to retain the anchor in a radially collapsed configuration for delivery of the sensor assembly to the implantation site.

10. The system ofclaim 8 wherein the socket has an inner diameter sized to frictionally retain the sensor using an interference fit.

11. The system ofclaim 8 wherein the retaining element is adapted to move distally relative to the first inner member so as to displace the sensor from the socket.

12. A delivery system for an implantable sensor assembly including a sensor and a self-expanding anchor, the system comprising:

an outer catheter having an internal diameter sized to receive the sensor assembly;

an elongate, tubular first inner member movable within the outer catheter and having a distal end portion terminating in a distal opening, the distal end portion sized to receive at least a portion of the sensor assembly for delivery of the sensor assembly to an implantation site; and

means slidable within the first inner member for releasably engaging the sensor.

13. The system ofclaim 12 wherein the first inner member is a generally tubular sheath, and wherein the distal end portion is sized to receive the sensor and the anchor for delivery of the sensor assembly to the implantation site.

14. The system ofclaim 13 wherein the anchor has a radially collapsed delivery configuration and a radially expanded implanted configuration, and wherein the distal end portion of the sheath is adapted to retain the anchor in the radially collapsed configuration for delivery of the sensor assembly to the implantation site.

15. The system ofclaim 13 wherein the distal end portion of the first inner member includes a socket adapted to releasably retain the sensor for delivery of the sensor assembly to the implantation site.

16. The system ofclaim 13 wherein the means for releasably engaging the sensor includes:

an elongate body having a distal end;

a plurality of deflectable jaw members extending distally from the distal end of the body and adapted to releasably engage the sensor; and

an actuating member slidably coupled to the body and adapted to deflect the jaw members to cause the jaw members to engage the sensor.

17. A method of implanting an implantable sensor assembly at an implantation location in a vasculature system of a patient, the sensor assembly including a sensor and a self-expanding anchor, the method comprising:

transvenously advancing a catheter into the vasculature system such that a distal end of the catheter is positioned proximate the implantation location;

advancing the sensor assembly through a lumen of the catheter to the implantation location, the sensor assembly releasably retained at a distal end of a delivery device including:

an elongate, tubular first inner member movable within the catheter and having a distal end portion terminating in a distal opening, the distal end portion sized to receive at least a portion of the sensor assembly for delivery of the sensor assembly to the implantation site; and

an elongate retaining element disposed within the first inner member;

deploying the sensor assembly from the distal opening of the first inner member with the retaining element releasably coupled to the sensor assembly; and

de-coupling the retaining element from the sensor assembly.

18. The method ofclaim 17 wherein advancing the sensor assembly includes advancing the sensor assembly with the anchor retained in a collapsed configuration within the distal end portion of the first inner member.

19. The method ofclaim 18 wherein deploying the sensor assembly includes retracting the first inner member relative to the retaining element to deploy the anchor from the distal opening of the first inner member.

20. The method ofclaim 17 wherein advancing the sensor assembly includes advancing the sensor assembly with the sensor at least partially retained within the distal end portion of the first inner member and the anchor retained in a collapsed configuration by the catheter.

21. The method ofclaim 20 and further comprising deploying the anchor from the distal end of the catheter.